PROFIL

TRAFFIC

WE have just had news, my esteemed Lucilius, ithat Pompeii, the celebrated city in Campania, hasbeen overwhelmed in an earthquake, which shookall the surrounding districts as well. The city, youknow, lies on a beautiful bay, running far back fromthe open sea, and is surrounded by two convergingshores, on the one side that of Surrentum andStabiae, on the other that of Herculaneum. Thedisaster happened in winter, a period for which ourforefathers used to claim immunity from suchdangers. On the 5th of February, in the consulship 2of Regulus and Virginius, this shock occurred,involving widespread destruction over the wholeprovince of Campania ; the district had neverbeen without risk of such a calamity, but had beenhitherto exempt from it, having escaped time aftertime from groundless alarm.

The extent of the disaster may be gatheredfrom a few details. Part of the town of Herculaneum fell ; the buildings left standing are veryinsecure. The colony of Nuceria had painful experience of the shock, but sustained no damage.Naples was just touched by what might have proveda great disaster to it ; many private houses suffered,but no public building was destroyed. The villas 3built on the cliffs everywhere shook, but without

221

222 PHYSICAL SCIENCE BK. vi

damage being done. In addition, they say, a flockof six hundred sheep was destroyed, and statueswere split open ; some people were driven out oftheir minds, and wandered about in helpless idiotcy.The plan of my present work demands a discussionof the causes of this, and the disaster itself fits in withour present inquiries (i.e. our discussion is opportunein view of the recent disaster). We must seek solacefor the anxious and dispel overmastering fear. Forwhat can any one believe quite safe if the worlditself is shaken, and its most solid parts totter to

4 their fall ? Where, indeed, can our fears have limitif the one thing immovably fixed, which upholds allother things in dependence on it, begins to rock,and the earth lose its chief characteristic, stability ?What refuge can our weak bodies find ? whithershall anxious ones flee when fear springs from theground and is drawn up from earth s foundations ?If roofs at any time begin to crack and premonitionsof fall are given, there is general panic : all hurrypell-mell out of doors, they abandon their householdtreasures, and trust for safety to the public street.

5 But if the earth itself stir up destruction, whatrefuge or help can we look for ? If this solid globe,which upholds and defends us, upon which ourcities are built, which has been called by some theworld s foundation, stagger and remove, whitherare we to turn ? What comfort, not to say help,can you gain when fear has destroyed all way ofescape ? Where, I say, is there any protection youcan trust? what is there that will stand as suredefence either of oneself or of others ? An enemyI can drive off from my city wall. The meredifficulties of approach to turrets set on the dizzyheights will stop the march even of great armies.

i WHOLESALE DESTRUCTION 223

From storm the harbour shelters us ; our roofs are 6able to withstand the whole force of clouds let loose,and the endless deluges of rain. Fire cannot pursue us if we run away from it. Against heaven sthreats in thunder refuges underground and cavernsdug out in the depths of the earth are of availthe fire of heaven does not pierce the ground,but is beaten back by the tiniest portion of thesoil. In time of plague we may change our placeof abode. No species of disaster is without somemeans of escape. Lightning has never consumedwhole nations. A plague-laden sky has drainedcities, but has never blotted them out.

But this calamity of earthquake extends beyond 7all bounds, inevitable, insatiable, the destruction of awhole State. Nor is it only families or householdsor single cities that it swallows ; it overthrowswhole nations and regions. At one time it hidesthem in their ruins, at another consigns them to thedeep abyss ; it leaves not a wrack behind to witnessthat what no longer is, once was. The bare soilstretches over the site of the most famous cities,and no trace is left of their former existence.Nor are there wanting those who dread most ofall this kind of death, in which they go down aliveinto the pit, houses and all, and are carried offfrom the number of the living : as if every formof death did not lead to the one goal. Among gnature s righteous decrees this is the chief, thatwhen we reach the end of life we are all on a level.It makes no difference, therefore, to me whetherone stone wound me to death or I am crushedbeneath a whole mountain ; whether the weight ofone house come down on me, and I expire beneaththe dust of its humble mound, or whether the whole

224 PHYSICAL SCIENCE BK. vi

world descend upon my head; whether I yield up thisbreath in the open light of day or in the vast abyssof the yawning earth ; whether I am borne downto those depths all alone or along with a great9 throng of perishing nations. To me it can make nodifference how great is the turmoil that accompaniesmy death ; the thing is everywhere just the same.

Wherefore, let us raise high our courage againstthat disaster, which can neither be shunned noryet foreseen. Let us cease to listen to the peoplethat have bid adieu to Campania since the timeof this disaster, and have removed to other districts, vowing they will never set foot in thatquarter again ! Who can guarantee them more

10 solid foundations in whatever soil they choose ? Allthe world is subject to the same fate. If it has notyet suffered from earthquake, it may ; perchancethis spot on which you stand in full security will berent this night, or even this day before night. Howcan one tell whether is better the state of the placeson which fortune has already spent her force or ofthose which are upheld meantime, but only forsome disaster to come ? We do greatly err if wesuppose any quarter of the world wholly exemptfrom this danger. All quarters are subject to thesame law. Nature framed nothing to be immovable.

11 Different things will fall at different times. Just as inlarge cities, now this house and now that leans overand has to be shored up, so in the world as awhole, now this part contains a flaw, now that.Tyre was once notorious for a disaster of the kind.The province of Asia lost at a single stroke twelveof its cities. Last year calamity overtook Achaiaand Macedonia, now the injury has fallen uponCampania, whatever be the nature of that force

i EARTHQUAKES UNIVERSAL 225

which thus assails us. Fate makes a circuit, payinga second visit to places she has long passed over.On some places her attacks are more rare, more 12frequent on some. Nothing is suffered to be quiteexempt from injury. Not merely we men, whoselife is frail and fleeting, but cities too, and the earth scoasts and shores, yea, the very sea falls underbondage to fate. And in face of this we promiseourselves permanence in the boons fortune bestows !we suppose there will be stability and endurance inhappiness, whose fickleness is greatest of all thingson earth ! While men promise themselves all things 13in perpetuity, it never enters their thoughts that thevery earth on which we stand is not permanent. Theflaws of the ground are to be found everywhere ;they are not peculiar to Campania or Tyre orAchaia. The earth coheres imperfectly, it suffersbreach from many causes ; permanent as a whole,it is subject to collapse in its parts.

II

WHAT am I doing ? I had promised to offercomfort in face of danger, and lo ! I threaten itsterrors on all sides. I tell you that there canbe no assured peace in what can suffer or causedestruction. But that very fact I regard as a solace,and, indeed, the most powerful of all. Fear is butfolly when there is no escape from it. Philosophydelivers the wise from fear ; even the unlearnedmay derive great confidence from despair. Youmust, therefore, regard the words addressed to thoseamazed by sudden captivity amid fire and foe asaddressed to the whole human race :

The one safety of the conquered is to hope for none.

Q

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2 If you wish to fear nothing, think that everything is to be feared ; consider by how slightcauses our life is dissipated. Neither food nordrink, nor waking nor sleeping, is healthful, exceptin due measure. One may soon realise thatwe are but puny, insignificant bodies, weak andunstable, that small effort is needed to compass ourdestruction. The only sufficiency of danger, doubtless, would be the earth s trembling, its suddendissipation, the rending of its surface into chasms !

3 Surely he sets a high value on his life who dreadsonly lightning, and earthquakes with their yawningabysses ; won t he allow himself to open his eyes tohis frailty and be afraid of choking on his phlegm ?Such, forsooth, is our constitution by birth, suchthe powerful frames we have obtained, such thesize we have grown to, that we cannot perish unlessthe four quarters of the world are moved, the

4 heavens thunder, and the earth subside ! Why, apain in a tiny nail, not even the whole nail, but alittle ragnail at the side, may finish us ! And I mustfear only the trembling of the world, when toothick a spittle will choke me ! I am to await withdread the removal of the sea from its place, or theoverflowing of an abnormal tide with its excess ofwater ; why, some ere now have been strangled bya drink that took a wrong course down the throat !What folly to be afraid of the sea when you know

5 that a single drop may kill you ! There is nosolace of death greater than the very liability todeath, no solace of all the terrors from without equalto the thought that there are countless dangerswithin our own bosom. What greater madness thanto collapse at the sound of thunder, and throughfear of lightning to creep under the ground ? What

ii DEATH UNIVERSAL 227

greater folly than to stand in fear of the earth s 6tottering and the sudden fall of mountains, or inroadsof the sea cast up beyond the shore, when deathis everywhere present and meets us on every side ?Nothing is so small as not to be strong enoughto compass the destruction of the human race.Great or unusual dangers ought not to unnerve us,as if they implied more mischief than a commondeath ; nay, rather when one must quit the worldand at last resign life, it should be a positive joy toperish by some grand cause. Die we must some- 7where, sometime. The ground you tread may standfirm, it may confine itself within its own bounds andnot be tossed about by any violence ; yet some dayI shall be beneath it. Does it really matter, then,whether I place it on myself or itself do ? It is rentby the irresistible force of some disaster ; it burstsand draws me into its immense depths. Whatthen ? Is death easier on the earth s level surface ?What reason for complaint have I if nature will nothave me lie in a place unknown to fame ? or if shelays on me a portion of herself? My friend, 8Vagellius, 1 in that famous poem of his, says finely:

If fall I must, I should desire to fall from the height of heaven, 2

We may adopt the language. If fall I must, let theearth be shaken at my fall ; not that one ought topray for a public disaster, but it is a great solaceof death to see that the earth is likewise subject todeath.

1 The name is doubtful, as is, indeed, the quotation also.

2 The sense may be : I would have the heavens fall along with me ; thismeaning would suit the context better.

228 PHYSICAL SCIENCE BK. vi

III

1 IT will be useful also to be assured that none ofthese things is the doing of the gods, and that themoving of heaven or earth is no work of angrydeities. Those phenomena have causes of theirown. It is not by special command that they putforth their rage, but, just as in our own bodies, thedisturbance arises from certain inherent imperfections ; at the moment when they seem to inflictinjury, they sustain it. Through our ignorance ofthe truth all these things are terrible, the more as

2 their infrequency increases our alarm. Familiaroccurrences seem less serious ; the unusual causesgreater terror. But why is anything unusual in ourestimation ? The reason is that we grasp themeaning of nature only superficially, and notrationally ; we dwell too exclusively on what shehas done, and do not consider what she can do.Accordingly, we pay the penalty of this neglect inour terror of things that we suppose unprecedented,when they are not really unprecedented, but merelyunusual. For instance, are not superstitious fearsinspired both privately and even for the safety ofthe State, if either the sun has been seen in eclipseor if the moon, whose obscuration is more frequent,

3 has partially or wholly been concealed ? And isnot this far more so in the case of such sightsas we have spoken of: torches driven athwartthe heavens, the sky on fire over the greater partof its extent, comets, mock suns, stars appearingin the daytime, the sudden passage of stars thatmark their trail with a bright light ? Our wonder

in EARTHQUAKES HAVE NATURAL CAUSES 229

at these is in no case free from fear. As thecause of the fear is ignorance, is it not worth whileto gain the knowledge that will dispel it ? Howmuch better it would be to inquire into the causesof the alarming sights, to bend, in fact, our wholemind to the task ? Nothing, surely, could be foundmore deserving than that, of having the mind senergies not only lent to it, but devoted to it.

IV

LET us ask ourselves, therefore, what it is that stirs ithe earth to its foundation, what moves a mass ofsuch weight, what it is that is stronger than theearth, and that in its violence can shake such aload. Let us inquire why at one time the earthtrembles, at another is loosened and sinks, andagain is divided into parts and opens a chasm ;or why on some occasions the intervals of destructionare prolonged, on others are suddenly cut short.What is the cause why it now consigns to itsdepths rivers of renowned greatness, and now causesfresh rivers to issue ? why does it sometimes openup springs of hot water, sometimes freeze them 2with cold ? and why at times are fires caused toshoot out through some hitherto unknown openingin mountain or crag, while sometimes well-knownfires, that have been famous for centuries, are suppressed ? The earthquake produces a thousandstrange sights, changing the aspect of the ground,levelling mountains, elevating plains, exaltingvalleys, raising new islands in the deep. What arethe causes that bring these things to pass ? Thatis a subject well worthy our discussion. What, you

2 3 o PHYSICAL SCIENCE BK. vi

say, will be the reward of our labour ? Thatreward, I say, which surpasses all others, the3 knowledge of nature. Among the many serviceablelessons to be derived from such researches, nofeature is more commendable than this, that man isthereby made to dwell upon the sight of his owngrandeur 1 ; the study is pursued, not in hope of gain,but from the wonder it excites. Let us inquire, therefore, what it is that brings about all this. Theinquiry is so fascinating to me that although longago in my youth I published a volume on earthquakes, I am anxious to make another trial of mypowers, and to see whether age has added anythingto my knowledge, or, at any rate, to my industry.

1 THE cause of earthquakes has been assignedvariously by different authorities to water, fire, air,and to the earth itself ; some assign it to a combination of several of the causes, others, to a union of themall. Certain writers have stated that it was plainto them that some one of these causes produced theearthquake, but it was not plain which. Let uslook at the various opinions in detail. First ofall, I feel bound to say in general terms that theold views are crude and inexact. As yet menwere groping their way round truth. Everythingwas new to those who made the first attempt tograsp it ; only later were the subjects accuratelyinvestigated. But all subsequent discoveries mustnonetheless be set down to the credit of those early

2 thinkers. It was a task demanding great courage

1 The meaning may rather be the grandeur of the subject.

v SCIENTIFIC DISCOVERY GRADUAL 231

to remove the veil that hid nature, and, not satisfiedwith a superficial view, to look beneath the surfaceand dive into the secrets of the gods. A great contribution to discovery was made by the man whofirst conceived the hope of its possibility. Wemust, therefore, listen indulgently to the ancients.No subject is perfected while it is but beginning.The truth holds not merely of the subject we aredealing with, the greatest and most complicated ofall, in which, however much may be accomplished,every succeeding age will still find something freshto accomplish. It holds alike in every otherconcern ; the first principles have always been along way off from the completed science.

VI

WATER is the first cause alleged: more authors than ione adopt this view, but it is not stated by all inthe same terms. Thales of Miletus is convincedthat the whole earth floats, and is upborne by moisture lying beneath it, which you may call either Oceanor the great sea, or still mere elemental water of adifferent character from the sea, the simple ingredient,moisture. In these waves, in his opinion, the globeis supported like some huge lumbering vessel in thewater which bears it. It is unnecessary for me to 2reproduce his reasons for supposing that the heaviestpart of the world cannot be sustained in such a rareand nimble element as air : for the earth s positionis not the question here but its movement. By wayof argument, to prove that water is the cause, headduces the fact that in every considerable earthquake, as a rule, new springs burst out. So if

232 PHYSICAL SCIENCE BK. vi

a boat leans over to one side away from the straight,the result is that it ships water. And, generallyspeaking, in the case of all objects which watersupports, if they are unduly sunk, the water eitherpours over them or at any rate rises to right andleft above its ordinary height.

3 Now, no lengthened consideration is neededto prove the falsity of this view. Why, if theearth were supported by water, and from timeto time shaken by it, it would be in perpetualshock ; the wonder would be not that it wastossed about sometimes, but that it was ever atrest. Then, again, it would be shaken all over andnot at a single point : we never find only half theship tossed by the waves. But, according to presentexperience, a shock never occurs over the wholeearth simultaneously, but is always felt at someparticular spot. How, then, can it be that what iscarried as a whole is not shaken as a whole, if theshock comes from the body by which it is carried ?

4 But, it may be urged, why do waters burst out atthe time of earthquakes ? Well, in the first place,there has often been earthquake without any freshsupply of water appearing. Secondly, if the supposed cause of the water rushing forth were thetrue one, it would pour all round the sides of theearth, as we see happening under similar circumstances in sea and rivers : when boats sink, theincrease of water shows itself chiefly over the sides.Finally, the outburst of waters which Thales describes would not be so small as he says, nor wouldit ooze in like bilge-water through a chink, but fromthe exhaustless reservoir that upbears all creation,a mighty deluge would ensue.

vii WATER AS CAUSE OF EARTHQUAKE 233

VII

SOME, who, like Thales, attribute earthquake to the ieffects of water, give a different explanation of itsoperation. There are, they say, many kinds ofwaters running over the whole earth. In oneplace there are constant rivers whose size rendersthem fit for navigation, even without the aid ofrains. There is the Nile, rolling down its hugevolume all summer long : here are the Danube andthe Rhine separating with their streams the peacefulfrom the hostile, the former checking attacks fromthe Sarmatians and forming the boundary betweenEurope and Asia, the latter keeping back theGermans, a nation ever keen for war. Then there 2are lakes of very wide extent, great pools surroundedby tribes mutually ignorant of each other, marshesthat no boat can struggle through, that cannot bepassed even by the people that dwell on theirborders. Add, then, the multitude of fountains, andof river sources that belch out of their recesses full-grown streams. Besides, there are many rushingtorrents that gather only for a time, whose force isas shortlived as it is sudden. Now there are waters,in all this variety of form and character, within as 3well as above the earth. Away there below some areborne along in vast bulk, and tumble their wholevolume down the steep : others more sluggish aredammed back in shallows, and flow with gentle, quietstream. And can any one deny that within thosevast underground hollows waters are formed, and liesluggish and inactive in many places? It needs nolong proof to show that there must be many waters

234 PHYSICAL SCIENCE BK. vi

in the place where all waters are. The earth wouldnot be able to produce so many rivers unless itpoured them from a copious reserve.

4 This being so, sometimes below the earth ariver must become swollen, and leaving its banksassail with violence all obstacles that meet it. Sothere will be a movement of some point on whichthe river has made an onset, and which it will keeplashing until its waters fall. Or it may happen thatthe constant wear of a stream may eat awaysome quarter, dragging down thereby some massabove, by whose fall, in turn, the surface which

5 rested on it is shaken. Now surely a man truststoo much to the sight of the eyes and cannot launchout his imagination beyond, if he does not believethat the depths of earth contain a vast sea withwinding shores. I see nothing to prevent or opposethe existence of a beach down there in the obscurity, or a sea finding its way through the hiddenentrances to its appointed place. There, too, itoccupies as much space as here, perhaps more,since the regions up on earth have had to be sharedwith so many living creatures ; but the hiddenregions being desert without inhabitant give freer

6 scope to the waves of the nether ocean. And whois there to hinder the sea from swelling there andbeing tossed by all the winds that every intersticeof the earth, and every species of atmosphere cancreate ? So, then, when a storm greater than ordinary has arisen, it may beat upon some one side ofthe earth with too great vehemence and move it.For on the surface likewise, many places whichhad been far from the sea have felt the violence ofits sudden approach : villas almost out of sight ofit have been invaded by the waves which used only

vii ABUNDANCE OF UNDERGROUND WATER 235

to be heard in the distance. The nether sea, too,can approach and retire ; neither of which movementscan take place without shock to the earth that standsabove it.

VIII

I DO not, indeed, suppose that you will long hesitate ito believe that there are underground rivers anda hidden sea. From what other cause could therivers burst out and come to the surface unless thesource of the moisture were shut up within theearth ? For instance, when one sees the Tigrisinterrupted and dried up in the middle of its course,not diverted as a whole, but gradually with imperceptible, losses first lessen and then waste away,where do you suppose it goes to if not to the depthsof the earth, especially as you see it emerge againnot less in volume than its former stream ? And 2what are you to say when you see the Alpheus, socelebrated by the poets, sink in Achaia and, havingcrossed beneath the sea, pour forth in Sicily thepleasant fountain Arethuse ? And don t you knowthat among the explanations given of the occurrenceof the inundation of the Nile in summer, one isthat it bursts forth from the ground, and is swollennot by rain from above but by water given outfrom within the earth ?

I have myself heard from their own lips the 3story told by the two non-commissioned officerssent to investigate the sources of the Nile by ourgood Emperor Nero, a monarch devoted to virtuein every form, but especially solicitous for theinterests of truth. The King of Ethiopia hadsupplied them with assistance and furnished letters

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of introduction to the neighbouring kings, andso they had penetrated into the heart of Africa

4 and accomplished a long journey. "We cameindeed," I give their own words, "to huge marshes,the limit of which even the natives did not know,and no one else could hope to know ; so completelywas the river entangled with vegetable growth, 1 soimpassable the waters by foot, or even by boat, sincethe muddy overgrown marsh would bear only asmall boat containing one person. There," my informants went on, " we saw with our eyes two rocksfrom which an immense quantity of water issued."

5 Now whether that is the real source or only anaddition to the river; whether it rises there ormerely returns to the surface after its previouscourse underground ; don t you think that, whateverit is, that water comes up from a great lake in theearth ? The earth must contain moisture scatteredin numerous places and collected at depth in orderto be able to belch it out with such violence.

IX

1 FIRE is the cause assigned by some for earthquakes,but they are not agreed as to its method of action.First among them is Anaxagoras, who is of opinionthat pretty much the same cause produces concussion in the earth as in the atmosphere. In the netherparts of earth, air (gas) causes explosions of thickatmosphere massed in clouds with the same violenceas on earth clouds are wont to be burst. Fire isstruck out by this collision of clouds and by the

2 rush of the atmosphere that is forced out. This fire

1 The so-called "sudd."

ix FIRE AS CAUSE 237

in seeking an exit meets obstructions and burststhrough all obstacles, until it has either found a wayof escape to the light through the narrow passages,or has made one for itself by violence and destruction. Other writers who still believe the cause to liein fire do not suppose that this is its method ofaction : they think the fire presents itself in morethan one place and burns away everything in thevicinity. Then if the parts eaten away fall in atany time, a shock follows in the portions which aredeprived of their supports ; they first totter and thencollapse ; nothing encounters them to support theirweight. Then chasms and vast gulfs are opened 3up, or it may be, after hanging a long time in thebalance, the ground settles down over what is stillleft standing. We see the same thing happen ordinarily as often as a part of the city suffers from a fire.The joists are burnt through, or what gave supportto the upper part of the buildings is undermined.Then the roofs after tossing about for a long timefall in ; their swaying and oscillating continue untilthey find a resting-place on solid ground.

X

ANAXIMENES affirms that the earth is itself the icause of the earthquake, and that nothing encountersit from without to give it a shock. Within it, hethinks, certain parts of its substance fall of themselves,either loosened by moisture, or eaten away by fire,or shaken off by the violence of air. But even inabsence of such active cause there is not wantingsufficient to account for the loss or removal of someportion of the earth. In the first place, all things

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fall through age, for nothing is safe from the ravagesof time, which waste even the solidest and strongestedifice. In old buildings parts fall without beingknocked off, merely because they have more weight2 than strength. So in the earth s body as a wholeit comes to pass that portions are loosened by age,and being loosened, fall, causing shock to the thingsabove them. This they do primarily while they areleaving their place ; for nothing, especially if it islarge, can be wrenched off without movement ofthat to which it adhered. But further, when theobjects have fallen, they meet the solid earth andrebound like a ball. When a ball falls, it jumps upand bounces repeatedly, just as often, in fact, asit recoils from the ground for a new flight. If theloosened objects within the earth are carried downinto stagnant waters, this accident of itself causesa shock to the vicinity through the wave cast upby the weight of the objects shot suddenly downfrom a great height.

XI

SOME attribute these earthquakes to fire, butgive different explanations of its action. Whenfire causes intense heat at various points beneaththe earth, it must roll up a great cloud of vapour,which can find no exit, and which dilates the airby its high temperature. If the pressure of thevapour is excessive, it scatters all obstructions ; butif it is comparatively moderate, it merely causesmovement of the earth. We observe water smokewhen fire is applied. What the fire does to thiswater in a narrow pot, one may suppose is doneon a much greater scale when a violent and wide-

xi AIR AS CAUSE 239

spreading fire causes immense extents of water toboil. It then by evaporation from the overflowingwaters shakes violently whatever it strikes.

XII

MANY of the greatest authorities are persuaded that iearthquakes are to be attributed to air. Archelaus,who is well versed in the records of antiquity, speaksthus : Winds are carried down into the earth shollows and recesses. When they are all full, and theatmosphere is condensed to the utmost extent, theair, which continues to come in, forces and thruststhe former air, and with frequent blows first compresses and then dislodges it. The air in its 2endeavour to find room forces all the narrowpassages and tries to burst its barriers. Throughthe struggle of the air as it seeks for an escapeit comes to pass that the earth is moved. Thisexplains why the approach of an earthquake ispreceded by still and quiet of the atmosphere ;the force of the air which is wont to rouse thewinds is held in check in its nether abode. Even 3on the present occasion of the earthquake inCampania, although the season was winter, theatmosphere was perfectly still and calm for severaldays before it. 1 Well, then, did an earthquakenever take place when there was a wind blowing ?On very rare occasions have there been two windsblowing simultaneously. Still, such a thing ispossible, and is wont to occur. But if we admitit as an established fact that two winds can bein activity at one and the same time, why shouldn t

1 The text is uncertain, and the argument down to the end of the chapterrather obscure.

2 4 o PHYSICAL SCIENCE BK. vi

it happen that [at times] one of them agitates theupper air, the other the nether ? l

XIII

1 IN this category you may rank Aristotle and hisdisciple Theophrastus, a man of pleasant though notof superhuman eloquence, as the Greeks consideredhim, and of easy, polished style. Let me unfold inmore detail what they hold in common : There isalways evaporation of some kind going on fromthe earth, which is at one time dry, at another hasan admixture of moisture. When this, rising fromthe lowest parts of earth, has been raised to theutmost extent, and has no place beyond into whichto issue, it is borne back and returns upon itself.The struggle of the air in its ebb and flow tossesto and fro all obstructions it meets, and, whetherits egress is stopped or whether it escapes throughthe narrow openings, it causes movement of the

2 earth and uproar. To the same school of opinionbelongs Strato, who made a special study of thisdepartment of science, and was a diligent studentof natural philosophy. His verdict on the matteris this : Cold and heat always move away fromone another in opposite directions, and cannotremain in the same place. Cold flows into thespot whence the influence of heat has departed ;and, conversely, there is heat in the place whencecold has been banished. The statement is beyonddoubt, but the contrariety of the two may become

1 The argument seems to be : Two winds can blow simultaneously. Onemay be beneath the earth (causing or during earthquake), one above.Therefore, stillness of the upper atmosphere is not a necessary concomitantof earthquake. The fact has at times been otherwise.

xni EFFECTS OF TEMPERATURE 241

plain to you from the following : In the winter 3season, when there is cold on the earth s surface,the wells are warm, and caves and all undergroundretreats equally so. The heat, yielding possessionof the upper regions to the cold, retreats downthere. When it reaches the lower regions, andis accumulated there to the utmost, the denser itis, the more powerful is it. To this a furthersupply is added, to which what has alreadygathered, and is compressed into a narrow space,of necessity gives way. The same thing happensfrom the opposite cause when a greater quantity ofcold is borne down to these recesses. All the heat 4that lurks there gives way to the cold, and retiresto the narrow passages, and is driven onward withgreat impetuosity. The nature of the two, as Ihave said, does not allow agreement, or abode inthe same place. In its flight, then, and eager hasteto escape at all hazards the air pushes back andtosses about all that lies near it. This is why,previous to an earthquake, a roaring is usuallyheard, through the tumult of the winds in theearth s bowels. For not otherwise, as our poet 5Virgil says, could

The earth bellow beneath our feet and the lofty peaks be moved,

were not this the work of the winds. In thiscontest again there are ups and downs. There arecessations in the massing of the heat and, in turn,in its emission. Then the cold, too, is restrainedand gives way, but some day soon it will be morepowerful again. While, therefore, the alternatingforces rush to and fro, and the air moves hitherand thither, the earth is shaken.

R

242 PHYSICAL SCIENCE BK. vi

XIV

1 THERE are some who think that, while air and noother cause produces earthquake, it operates in adifferent way from that which Aristotle supposed.Listen to what they say : Our body is irrigatedwith blood, and with air which courses everywherealong its own routes. We have some comparatively narrow vessels through which they cannotdo more than pass ; some wider, in which theyaccumulate, and from which they are distributed

2 to the members. So this whole body of the earthat large has passages alike for water, which performsthe function of blood, and for wind, which mightbe called simply the breath of its life. These twoencounter each other at some points, at some pointsthey are stationary. While in our bodies goodhealth is enjoyed, the movement of the veins preserves its rate undisturbed ; but when there ismalady the pulse beats more rapidly, the deepbreathing and panting betoken laboured, weariedeffort. In like manner the earth remains unshaken

3 while it maintains its natural position. But if anyflaw occur in it, there is a shaking, just as of abody suffering from disease ; for the air whichflowed through it with regularity is violentlysmitten, and causes its veins to quiver ; but not,let me add, in the way, described a little above, 1imagined by those who will have it that the earthis a living creature. In that case the earth, justas an animal does, would feel the agitation equallyall over. When a fever seizes any of us, it does

1 There seems a slight lapse of memory here. Cf. pp. 126, 196.

xiv EFFECTS OF AIR 243

not delay for a time its attack upon some parts,but with uniform regularity spreads over them all.

Perhaps you had better assume, therefore, that 4air from the surrounding atmosphere enters the earth.As long as it has free egress, it glides through itwithout doing harm ; but if it meet some obstacleto block its way, then it is, to begin with, weightedwith the atmosphere that pours in on the rear ;by and by it escapes with difficulty through somechink, and makes its way with the greater violencethe narrower the opening is. That cannot takeplace without a struggle, and a struggle involvesshaking of the earth. But if the confined air 5cannot find even a chink by which to issue, it ismassed and becomes furious, and is driven round inthis direction and in that, overthrowing or burstingone thing after another. It is excessively subtle,and at the same time exceedingly powerful ; it canworm its way into obstructions however great,splitting and scattering whatever it enters. Whenthis occurs, then there is a regular tossing of theearth. For the earth either opens to give roomto the wind, or, after giving room, is deprivedof its foundation and subsides into the very cavernfrom which it allowed the wind to issue.

XV

SOME entertain the following opinion : The earthis porous at many points, possessing not merelythose first shafts which it received as ventilatorsat its creation, but many subsequently opened upby various changes. In some places water haswashed away the soil that was on the surface ;

244 PHYSICAL SCIENCE BK. vi

part has been eaten away by torrents, while partshave been exposed by the disruptive action of greattides. Through the interstices thus produced airenters. If it so happen now that the sea hasshut it in and driven it deeper, and the wavesprevent its escape by the same road, egress andregress being alike closed, the air rolls aboutwithin the earth. Its natural tendency is to hurrystraight forward, but as that path is closed, itpresses upward and lashes the earth, whose weightlies heavy upon it.

XVI

1 I MUST further mention a view held by the majorityof writers, which probably I shall myself support.The earth does not lack air within ; that everybodyknows. I do not mean merely the air which holdsit together and unites its parts, which exists even instones and dead bodies ; but I mean that fresh vitalair which supports all life. Unless the earth possessed this store of air, how could she infuse it intoso many trees and crops, which derive their life from

2 this and no other source ? How could she nourishall the different roots that sink into the soil in oneplace and another, some merely attached to the surface, others sunk deeper, had she not an abundantsupply of the breath of life, which produces so manyvaried growths and rears them with its nourishingdraught ? These are the slighter arguments that Ihitherto urge. Why, all the heaven we see, whichis shut in by fiery ether, the highest portion of theuniverse, all these stars, whose number cannot beconceived, all this concourse of heavenly bodies,and, to mention only one more, this sun, that urges

xvi AIR NOURISHES THE UNIVERSE 245

his course so close to us, many times larger thanthe whole circuit of the earth all these drawtheir nourishment from materials of earth whichthey share among them, and are sustained, ofcourse, by nothing else than the breath of the 3earth. This is their nourishment, this their pasturage. Now the earth would be unable to nourishso many bodies of such size, larger even thanitself, unless it were full of breath, which it exhalesfrom every part of it day and night. For theremust be a large reserve of that from which somuch is sought and taken ; in fact, the supply to bedrawn from it is created for the occasion. The 4earth would not possess a perennial supply ofair sufficient for the wants of so many heavenlybodies, unless the elements issued and returnedalternately and were transmutable into one another.But apart from this, it is necessary that the earthbe abundantly filled with it, and be able to drawit forth from her hidden store. There is nodoubt then that a great quantity of air lurksin the interstices of the earth, and a widelydiffused atmosphere occupies the hidden spacesunderground. If that is true, of necessity theearth must often be moved, since it is full of a mostmovable substance. No one, I suppose, can doubtthat there is nothing so restless, so capricious, sofond of disturbance as air.

XVII

IT follows, therefore, that air should obey the law ofits being ; what is wont to be moved will sometimesmove other things. And when ? Whenever its freecourse is checked. As long as it is not hindered it

246 PHYSICAL SCIENCE BK. vi

flows quietly along. When it is opposed and heldback it becomes furious, bursting all obstacles justlike that

Araxes that ever spurned a bridge.

2 As long as the river has a free easy channel itrolls down its waters in due and regular succession.But if through chance or by human agency rocks areplaced in its way to check its course, then it gathersfresh strength from the barrier, and the morenumerous the obstacles opposed to it, the greaterthe force that it musters to overcome them. Forall the water that accumulates behind, constantlyincreases, and being at last unable to bear its ownweight manifests its violence through the havoc itworks in its descent, and escapes headlong down itschannel, bearing the very obstacles that blocked its

3 path. The same thing occurs with air, only that, inproportion to its greater strength and mobility,it is the more rapidly carried onward, and burststhe more violently all that encloses it. From this,of course, there is a disturbance in the part of theground under which the struggle has occurred. Thetruth of this assertion may be proved from the consideration that often when an earthquake has takenplace, involving a breach of only some part of theearth, wind has issued from it for several days.

4 This is recorded to have taken place in the earthquake in which Chalcis suffered, as you will findin Asclepiodotus, Posidonius pupil, in his discussion of my own topic of Physical Inquiries. Inother authors, too, you will find it stated that aftera chasm had opened up at one spot, in no long timewind issued from it, having no doubt made for itselfthe way along which it travelled.

xvin CHIEF CAUSE OF EARTHQUAKE 247

XVIII

THE chief cause of earthquake, therefore, is air, ian element naturally swift and shifting fromplace to place. As long as it is not stirred, butlurks in a vacant space, it reposes innocently,giving no trouble to objects round it. But whenany cause coming upon it from without rouses it, orcompresses it, and drives it into a narrow space,in the first instance, to be sure, it merely retiresand roams about, its enclosure. But when opportunity of escape is cut off, and resistance meets iton all hands, then

which, after long battering, it dislodges and tosseson high, growing the more fierce, the stronger the 2obstacle with which it has contended. By and by,when it has traversed the whole space in which itwas enclosed, and has failed to find a way of escape,it recoils from the side on which its impact wasgreatest. It is then either distributed throughthe secret openings which the earthquake of itselfcauses here and there, or escapes through a newrent. So uncontrollable is this mighty power. Nobolt can imprison wind ; it loosens every bond,bears with it every weight, and insinuating itselfinto the smallest crannies wins its release ; for bythe invincible power of nature it is free, especiallywhen roused, and asserts its right for itself. Air is 3a thing no man can tame ; nothing will be foundwhich,

248 PHYSICAL SCIENCE BK. vi

When the winds struggle and the tempests roar,

Can restrain them by its sway and rein them by bonds and prison.

Doubtless the poets wished the place in whichthe winds lay pent up underground to be considered a prison. But they did not perceive eitherthat what was shut up is no longer wind, orthat what is wind can no longer be shut up.What is shut up is at rest, and the atmosphereis at a standstill ; whereas all wind is in flight.4 Besides these arguments, there is a consideration by which it becomes manifest that motionis brought about by air, namely, that our bodiesnever tremble except when some cause producesdisturbance of the internal air, 1 which is contractedby fear, grows sluggish in old age, languishes whenthe veins are numbed, is checked with cold, orafter some attack of fever is quite driven from itswonted course. As long as it flows unimpeded, andmoves in its wonted fashion, there is no quiveringof the body. When anything intervenes to preventits functioning, then being no longer able to maintain what it upheld by its vigour, it fails, causing acollapse of everything that it had sustained whenunimpaired.

XIX

1 WE must now hear what Metrodorus of Chiosdesires to urge by way of opinion. I do not allowmyself the liberty of passing over unnoticed evenopinions that I disapprove ; it is better to have thelargest possible variety of views, and to condemn

2 rather than omit what we do not approve. Well,then, what has Metrodorus to say ? He compares the

1 Or spirit : there is almost a play upon the ambiguous meaning of theterm.

xix SUBTERRANEAN VOIDS 249

subterranean disturbances to the voice of a personwho puts his head into a barrel and begins to singout. In that case there is a kind of quaveringas the voice extends and resounds through thewhole hollow space ; slight as the movement is, itpasses all round the vessel in which it is enclosed,grazing its sides and causing disturbance all through.In the same way the vast empty caverns thatstretch down beneath the earth have atmosphereof their own, on which other air coming from abovefalls with violence. The agitation produced differsin no wise from that of the empty vessels which Ihave just mentioned, when they resound throughshouting into them.

XX

LET us now go on to consider the authors who ihave alleged as causes all the different factorsmentioned, or, at any rate, several of them.Democritus is one of those who think that severalare concerned. He asserts that the earthquake isproduced sometimes by air, sometimes by water,sometimes by both. He pursues the argumentin the following way : Some portion of the earthis hollow, in which a large quantity of water hasgathered. Part of this water is thinner and lessdense than the rest. When it is driven back bya heavy mass descending upon it from above, itcomes violently against the earth, causing a commotion of it. The fluctuating movement of thewater cannot take place without correspondingmovement of the body on which it impinges.Besides, what we said a little above regarding air 2

250 PHYSICAL SCIENCE BK. vi

must be repeated in regard to water. When itis accumulated at one place, which becomes toosmall to contain it, it inclines in some particulardirection, and opens up a passage for itself, atfirst by its mere weight, afterwards by the gatheringforce of its current. Being long shut up it cannotescape except down an incline, and it cannot dropstraight down with any gentleness, or without violentshaking of the parts through which and on which it

3 falls. Now, if after it has begun its rapid downwardmovement it is checked at any point, and the forceof the current is thrown back upon itself, it is drivenback on the earth which encounters it, and attacksthe earth at the point where it is most insecure.Moreover, the ground is sometimes so saturatedwith the moisture it has received into its heart thatit subsides to a lower level and its very foundationis destroyed. The pressure is then exerted on thepart toward which the weight of the descendingwaters most inclines. Air, too, sometimes urgesthe water. If it presses with some degree ofviolence, it naturally moves the part of the earthtoward which it has urged the gathering of the

4 waters. Sometimes, again, the air is driven intopassages through the earth, and in its searchfor a way of escape causes a general movement.The earth, as we know, is pervious to wind ; airis too subtle to be excluded, too violent to be resistedwhen excited to rapid movement.

Turning from Democritus to Epicurus, we findthe latter to assert that all the foregoing may becauses of earthquake, but he tries to introducesome additional ones. He criticises other authorsfor affirming too positively that some particularone of the causes is responsible, as it is difficult

xx CO MB IN A TION OF CA USES 2 5 1

to pronounce anything as certain in matters inwhich conjecture must be resorted to. As he says, 5then, water is capable of producing earthquakeby washing and rubbing off certain portions, theweakening of which removes the support of whatwas upborne by them when unimpaired. Theforce of air is also capable of moving the earth.Perhaps the air within the earth is set in violentagitation by other air entering from without. Or,perchance, it may be that the earth receives aninternal blow from the sudden fall of some portionof it, and derives thence the shock. Or, perchance,some portion of the earth is upheld, as it were, bycertain pillars and stakes, the injury or withdrawalof which causes a tremor to run through the massthey support. Or, perchance, a quantity of hot air eturning to fire and assuming the character of lightning courses along to the widespread destructionof all obstacles it encounters. Or, perchance, somewind stirs the sluggish marshy waters, whose strokein consequence shakes the earth ; or the tossingof the air, increasing to violence through the meremovement, is carried from the lowest depths rightup to the surface of the earth. Still, Epicurus issatisfied that there is no more potent cause of earthquake than air.

XXI

WE Stoics also are convinced that it is only air that ican attempt such a feat as the production of anearthquake, for than it nothing in the whole realmof nature is more powerful, more energetic ; inabsence of it even the elements that are most violentlose their force. It is by air that fire is kindled ;

252 PHYSICAL SCIENCE BK. vi

if you withdraw wind, water is sluggish. Waterbecomes impetuous only when the blast tosses itwith violence. This force it is that has power toscatter vast spaces of earth, to raise from thedepths new mountains, and to set in mid -ocean

2 islands hitherto unseen. Can any one doubt thatThere and Therasia and this island which in ourdays under our very eyes rose out of the AegeanSea, were carried up to the light by the force ofair ?

Posidonius will have it that there are twodifferent varieties in the movements of the earth,each with its distinctive name. The one is aquaking when the earth is shaken and moves upand down ; the other is a tilting when, like a

3 ship, it leans over to one or other side. I am ofopinion that there is still a third variety, which wehave a special term to denote. Our forefathers hadgood reason for speaking of a trembling of theearth, for it is unlike either of the other kinds ofmovement. On such an occasion things are neitherall shaken nor all tilted, but they quiver. In a caseof this kind no great damage is usually done ; while,on the other hand, a tilting is far more destructivethan a shock ; for unless a contrary movement setin very quickly from the other side to restore thelevel, downfall follows of necessity.

XXII

THESE movements being dissimilar, their causes arelikewise different. Let us deal first with the shakingmovement. If great loads are being conveyed bya row of many waggons, and the wheels, under

xxii EARTHQUAKES THAT SHAKE 253

the unusual strain, fall into the ruts of the road, onefeels the earth shaken. Asclepiodotus has put iton record that on one occasion the fall of a rockthat was torn off from the mountain-side causedby the tremor the collapse of some houses in itsvicinity. Just the same thing may occur beneaththe earth ; parts of the overhanging crags maybe loosened and fall with great weight and noiseupon the floor of the cavern beneath, and with aviolence proportionate to the weight of the massand the height of the fall. The whole roof of thesubterranean valley is disturbed by an occurrenceof this kind. It is conceivable, too, that rocks are 2not always wrenched off by their own weight ; whenrivers roll over them, the constant moisture weakensthe joints of the stone, and day by day bears awaypart of its fastening, causing abrasion, so to speak,of the skin in which the stone is enclosed. The longwaste of ages, through constant daily rubbing, byand by so weakens the fastenings that they ceaseto be able to sustain their burden. Then blocks 3of vast size fall down, then the crag hurled headlong will not suffer anything to stand that it strikesin the rebound from its fall, but

Comes away with a roar ; and all things seem suddenly to rushheadlong,

as our- countryman Virgil says. Such must be thecause of the earthquake that shakes the groundbeneath. Now I must pass on to the second kind.

XXIII

THE earth is naturally full of cavities, containingmuch empty space. Through these cavities air

254 PHYSICAL SCIENCE BK. vi

roams. When an excessive quantity has enteredand cannot escape it shakes the earth. This explanation is approved by others, too, as mentioneda little above. Perhaps the crowd of witnesseswill impress you. The view has the adhesion ofCallisthenes, and he is a man not lightly to beset aside. He was endowed with a lofty intellect,and he dared to brave the wrath of a king. Hisdeath is an eternal blot on the memory ofAlexander, which no valour and no success in

2 war can ever remove. As often as it is said,Alexander slew many thousands of the Persians,the retort will be, And Callisthenes too. As oftenas it is said, He slew Darius, in whose hands therewas then a mighty kingdom, the retort will be,Yes, and Callisthenes too. As often as it is said,He conquered all lands right up to the Ocean, theOcean likewise he essayed with fleets strange toits waters, from a corner of Thrace he extendedhis empire to the bounds of the East ; it willalso be said, Yes, but he slew Callisthenes.

3 Granted that he surpassed all former precedents ofgenerals and kings, yet of all that he did, nothingwill match his guilt in slaying Callisthenes.

Well, this Callisthenes, in the treatise inwhich he gives details of the sinking of Heliceand Buris, and discusses the disaster which sentthem into the sea, or the sea into them, sayswhat I have said at a previous point. Air, hesays, enters the earth by hidden openings under

4 the sea, just as everywhere else. By and by,when the path is blocked by which it haddescended, and the resistance of the water in therear has cut off its retreat, it is borne hither andthither, and encountering itself in its course it

xxin ACTION OF AIR 255

undermines the earth. That is the reason whyland over against the sea is most frequentlyharassed by earthquakes ; and hence it is thatNeptune has been assigned this power of movingthe earth. 1 Any one who has learned the elementsof Greek knows that he is called among the GreeksEarthshaker

XXIV

I SHALL be ready to allow that air is the cause of ithis form of destructive earthquake. But I shallhave some criticism to offer as to the method bywhich it enters the ground. Does it enter byfine openings that the eye cannot detect, or bylarger and more evident ones ? Does it come fromthe depths of the earth, or does it pass throughthe surface too ? The last-mentioned view seemsinconceivable. In our bodies the skin keeps outair, which finds no entrance except that throughwhich it is inhaled. And even when taken in byus, it cannot settle except in the looser portion ofthe body. It does not remain among the sinews 2or muscle, but in the bowels and the open vesselsof our internal organs. The same arrangement maybe suspected in regard to the earth s interior from thevery fact that the movement in an earthquake is noton the surface of the earth or about the surface, butbeneath in the lowest parts. A proof of this is thatseas of immense depth are tossed up, no doubtfrom the movement of the ground over which theyspread. It is therefore probable that the earth 3is moved in its depths, and that the air is formed

there in the immense caverns. Nay, says somecritic, but just as when we shiver from cold atrembling follows, so, too, the earth is shaken byair affecting it from without. This I deny canby any possibility occur. Why, the earth mustget a chill in order to have the same happen toit as to us, w r hom an external affection drives into

4 a shuddering fit. I should quite allow that theearth shows symptoms of much the same kind aswe do, but the cause is wholly different. An injuryof a deeper kind, more toward its centre, must affectit, the very strongest proof of which may be foundin the fact that when through violent earthquakethe soil is laid open in wide destruction, thechasm sometimes takes in and buries whole cities.

5 Thucydides tells us that, about the time of thePeloponnesian War, the island of Atalanta, eitherwholly, or, at any rate, for the most part, wasswallowed up. You may take Posidonius forwitness that the same thing happened to Sidon.But we do not require evidence of this. Withinour own memory the earth has been torn byinternal movement, adjoining places have beenrent asunder, whole plains have disappeared. I willnow explain how I suppose this sort of thing tooccur.

XXV

WHEN air has completely filled a large vacant spacewithin the earth, and has begun to struggle andmeditate escape, it lashes again and again the sidesof the enclosure within which it lurks, and right overwhich, as it happens, cities are sometimes situated.The shaking is at times so violent that buildings

xxv FAMOUS EARTHQUAKES 257

standing above the area of disturbance are throwndown. Sometimes it goes to such lengths thatthe walls by which the whole roof of the cavern issupported fall right down into that vacant underground space, and cities sink entire into theunfathomed depths. Long ago, if one may believe 2the story, Ossa and Olympus were united; subsequently they were separated by an earthquake, andthe one great mountain was split into two. Thenthe Peneus made its escape, draining the marsheswith which Thessaly was overspread, and drawingoff the waters, which from want of exit had hithertoformed a lake. It was an earthquake that let looseLadon, the river which flows between Elis andMagalenopolis. What, it is asked, do these factsgo to prove ? Simply that air gathers in the spacious 3caves for what other name can I apply to theempty places under the earth ? Were this not so, 1great spaces of the earth would be convulsed, andmany of them would totter to ruin at one and thesame time. As it is, only small portions suffer, nordoes a shock ever extend as much as two hundredmiles. Look at the recent one, the marvellous talesof which have filled the whole world ; it did notpass beyond Campania. Need I say that when 4Chalcis felt the earthquake shock Thebes did notfall ? when Aegium suffered, Patras, which is quiteclose by, only learned by report about the earthquake ? That mighty shock, which swallowed upthe two cities Helice and Buris, stopped shortof Aegium. Plainly, then, the movement extendsonly such distance as the empty space undergroundstretches.

1 I.e. were the air distributed all through the earth.

258 PHYSICAL SCIENCE BK. vi

XXVI

1 To prove my point I might have used, somewhat unfairly perhaps, the authority of the great writers whorelate that Egypt never experienced an earthquakeshock, the reason they allege for it being that it isall composed of mud. If one may believe Homer,Pharos used to be as far from the mainland as a shipunder full sail could reach in a day s voyage ; but ithas now become attached to the mainland. TheNile s swollen stream brings down great quantities ofmud, and by adding it from time to time to the existingland it has by an annual increase constantly carried

2 forward the coast of Egypt. The country thus iscomposed of rich loamy soil without interstices, asit has become solid just by the drying up of the mud.The composition of the mud was close and firm,the particles of it being stuck together ; no vacantspace could intervene, since the solid was alwaysbeing added to by the liquid and soft slime.But Egypt is, as a matter of fact, subject to earthquake ; and Delos, too, though Virgil bade it standfast,

And granted that it should be a settled land of tillage, and shouldlaugh the winds to scorn.

The philosophers, too, a credulous set of people,relying on Pindar s authority, said that it did notexperience movement. Thucydides asserts thatin former times it was unshaken, but sustained ashock about the time of the Peloponnesian War.

3 Callisthenes asserts that the same thing happenedon another occasion also. Among the numerousportents these are his words by which warning was

xxvi THE SEA NO PROTECTION 259

given of the overthrow of the two cities Helice andBuris, the most remarkable were the appearance ofa huge pillar of fire and the earthquake shock inDelos. Yet he will have it that the island is comparatively firm for the reason that it is placed on thesea and has hollow crags and porous rocks, whichafford a way of escape to air imprisoned in them.For this reason, too, islands have, he thinks, a 4firmer soil, and cities are safer in proportion totheir proximity to the sea. The falsity of such anopinion surely Pompeii and Herculaneum learnedto their cost. Add now the fact that every sea-coast is particularly subject to earthquakes. Paphos,for instance, was more than once ruined, and thefamous Nicopolis is already intimately acquaintedwith this mischief. Cyprus is surrounded by adeep sea, but is subject to shocks. Tyre is asregularly shaken by earthquake as it is washed bythe waves. Such, then, are for the most part theexplanations that have been suggested for thetrembling of the earth.

XXVII

WE must now essay an explanation of certain ipeculiar features which are said to have occurred inthe recent Campanian earthquake. A flock of sixhundred sheep is asserted to have been killed in thedistrict near Pompeii, and there is no reason tosuppose that this happened to the sheep throughfright. We have said that after great earthquakesit is usual for a pestilence to occur. And nowonder, since in the depths of earth many deadlypoisons lurk. In fact, the very atmosphere there, 2

260 PHYSICAL SCIENCE BK. vi

being stagnant through some fault in the earth orthe sluggish movement and the everlasting darknessthat prevails, is dangerous to breathe. Or beingpoisoned by the fumes of the internal fires, when itis released from its long inactivity, it taints andpollutes this pure clear air above, and brings newforms of disease to those who inhale the unwonteddraught. You remember, too, that we found thewater lurking in the secret depths to be uselessand even pestilential, since activity never stirsit, and the free breath of heaven never ruffles it.

3 Being therefore thick and covered beneath grosseternal darkness it contains only elements that arepestilential and injurious to our bodies. So, too, theatmosphere, which mingles with it and lies amidthese marshes, scatters far and wide its poison whenit issues out, and kills those who breathe it. Theflocks, which the pestilence is wont to attack, feelthe poisonous effects more readily, because they aremore greedy in feeding. They live for the mostpart in the open, and they drink a great deal ofwater, which is chiefly responsible for the pestilence.

4 Sheep are of rather delicate constitution, and, asthey keep their heads close to the earth, I am notsurprised at their being attacked by the infection ;they receive the blasts of tainted air just as it issuesfrom the ground. If it had issued in greater volume,it would have injured man too. But the abundantsupply of pure air counteracted it before it couldrise high enough to be breathed by any humanbeing.

xxvin POISONS UNDERGROUND 261

XXVIII

Now you may infer that the earth contains many ideadly elements from the mere fact that so manypoisons grow of themselves without being sown ;the soil no doubt contains seeds of evil as well as ofgood. Is it not the case that, earthquakes apart,in several places in Italy a pestilential steam isemitted through certain openings, which it is notsafe for either man or beast to breathe ? Even birds,if they meet it before it is neutralised by the purerbreath of heaven, fall in mid -flight ; their bodiesbecome livid, and their jaws swell just as if they hadbeen strangled. As long as this air is contained in 2the earth and escapes by a narrow opening, it has nogreater power than to kill creatures that look downinto, or voluntarily approach too near, it. But whenfor centuries darkness has brooded over it, and thegloom of the place has increased the infection, itbecomes more dangerous through mere lapse oftime ; the more sluggish it is, all the more deadlydoes it become. Then when it has gained an exit itlets loose all that mischief conceived in the coldshades through endless ages of nether darkness,tainting with it the atmosphere of our realms ofearth. The better is ever conquered by the worse. 3Even that purer air of heaven then changes topestilential. Thence come sudden and continuousdeaths, and portentous forms of disease that springfrom unexampled causes. The disaster is long orshort lived, according to the strength of the sourcesof infection. Nor does the plague cease until thefreedom of heaven and the tossing of the windshave banished l that fatal air.

1 Or purified.

262 PHYSICAL SCIENCE BK. vi

XXIX

1 THROUGH fear some people have run about asif distracted or mad. For fear, even when inmoderation and confined to individuals, shattersthe mind s powers. But when there is publicalarm through fall of cities, burying of wholenations, and shaking of earth s foundations, whatwonder that minds in the distraction of sufferingand terror should have wandered forth bereft ofsense ? It is no easy matter in the midst ofovermastering evils not to lose one s reason. Soit is, as a rule, the feeblest souls that reach such

2 a pitch of dread as to become unhinged. No one,indeed, has suffered extreme terror without someloss of sanity ; one who is afraid is much like amadman. But some quickly recovering from thealarm regain self-possession. Others it moreviolently disturbs and reduces to sheer madness.Hence during times of war lunatics are to be metwandering about. On no occasion will one findmore instances of raving prophets than when mingledterror and superstition have struck men s hearts.

I am not surprised that a statue is split by anearthquake, after I have recounted that mountainshave been separated from mountains and the grounditself burst asunder down to its depths.

3 These places, once convulsed by the force of vast ruinSuch the power of change in the lapse of lengthened ages !Leaped asunder, they tell us, whereas hitherto both landsWere one ; into their midst rushed the deep with its mighty

billows,

Cutting off the Italian from the Sicilian side ; fields and citiesWere parted in sea-line and washed by the narrow tide that

flowed between.

xxix STATUES AND KINGDOMS SPLIT 263

One sees whole regions torn from their place, andwhat was once contiguous, now lying beyond the sea.One sees a separation of cities and nations when apart of nature is roused by internal motion, or the seaor fire or air has assailed some point ; for their forceis marvellous, since it has a boundless reserve fromwhich to draw. Though its rage is vented at but one 4point, yet it has the world s whole strength to reinforce its wrath. Thus it was that the sea tore awaySpain from the mainland of Africa. Thus it wasby the flood, which the greatest of poets havecelebrated, that Sicily was cut away from Italy. Themovements that proceed from depth have much moreforce. They are more energetic, as their effort isconcentrated upon a narrow area. Enough hasnow been said to show what mighty deeds theseearthquakes have wrought and what wondrous sightsthey have displayed.

XXX

WHY, then, should one be amazed that the bronze iof a single statue is burst, and that, not even solid,but hollow and thin ? as likely as not air in seekingan escape has got enclosed in it. And does notevery one know that buildings are sometimes observed in time of earthquake to split at the cornersand be united again ? Other things badly set upontheir base, and loosely and carelessly put togetherby the workmen, have been known to be weldedfirmly together by the repeated shaking of theearthquake. If it splits whole walls and whole 2houses, and rends the sides of great towers, whichare constructed of solid masonry, and scatters thepiles that support the foundations of great works,

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why should one think it worthy of remark that astatue had been cut equally into two from base tosummit? But why, it may be asked, did the shock last3 for several days ? For Campania went on tremblingcontinuously, more gently it is true, but still causinggreat damage, because what it shook was alreadyshaken and crushed. Things stood so insecurely asto require only a slight shake, but not a push, tobring them down. The explanation of the prolongedshaking is no doubt that all the air had not yetescaped, but though the greater part was discharged,a remnant was still roaming about here and there.

XXXI

THERE is yet a further proof that you may unhesitatingly add to the others that go to show thatall these phenomena are the outcome of air. Afterthe most violent shock that cities and provinces canexperience has spent itself, another of like violencecannot immediately follow ; after the crisis thereare only slight shocks, just because the most violentone has opened a way of escape for the strugglingwinds. The remains of the air that is left have notthe same power, nor do they require to struggle ;they have now found a way of escape, and follow thepath by which the first and greatest shock issued.

I am of opinion, too, that the observations of acertain learned and grave philosopher of my acquaintance deserve to be put on record ; he happenedto be taking a bath when the earthquake occurred.He asserted that he saw the tiles with which thefloor of the bathroom was paved, separate onefrom another and unite again. At one moment,

xxxi A PHILOSOPHERS OBSERVATIONS 265

when the pavement opened, the water was takenin through the joints, the next, when the pavementclosed, it was forced out all bubbling. I have heardthe same learned man relate that he had seen softmaterials undergo more frequent but more gentleshocks than materials naturally hard.

XXXII

So much, my esteemed Lucilius, with respect to the imere causes of earthquakes. Now we must adducesome considerations that will tend to reassure us inface of the perils of earthquakes. After all, it concerns us more closely to acquire resolution of mindthan erudition, and yet the former cannot be hadwithout the latter. Assurance comes to the mindfrom no source but elevating studies and the contemplation of nature. Is there any one, I say,that reflects upon causes, who will not be reassuredand emboldened by this late catastrophe in Campania to face disasters of all kinds ? Why should 2I fear man or beast, bow or lance? Far greaterperils are ever lurking for me. Lightning and earthshock, and all the great forces of nature, aim theirblows at us. Death must therefore be resolutely lchallenged whether its attack be with vast 1 overpowering onset or by ordinary means of daily occurrence. It is of no moment how threatening itsapproach, or how great the engine it brings upagainst us. The life it asks of us is a very littlething. It will be taken from us by old age, or by 3a little pain in the ear, or by a superabundanceof tainted moisture within, by food that the stomach

1 It would seem that ingenti and aequo have by some means got transposed in the ordinary texts. Gercke reads saevo for aequo.

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cannot assimilate, or by a slight injury to one s toe.Man s life is a paltry affair, but a mighty affair isthe contempt of life. He who can despise life maylook unmoved upon the tossing of the sea, eventhough all the winds have roused it, even thoughby some upheaval of the world the tide has turned

4 the whole Ocean bodily upon the land. Unmovedhe will behold the fierce forbidding aspect of thethundering heavens, yes, though heaven itself becrushed and unite its fires for the destructionof mankind and of itself first of all. Unmovedhe will behold earth s framework rent and earth sfoundations yawning beneath. Though the realmsof the nether world be uncovered, he will standover the abyss still dauntless, and into the pit intowhich he is doomed to fall he will perhaps leap.What is it to me how great the powers by whichI perish ? To perish is itself no great matter.

5 Wherefore, if we desire to be happy, to beharassed by no fear either of men, or gods, orcircumstance, to despise fortune with her superfluous promises and her contemptible threats, ifwe desire to live the peaceful life, and to vie withthe very gods in happiness, then we must carryour life in our right hand. Whether snares ordiseases attack it, the swords of foes or the crashof falling tenements, or the downfall of earth itself,or the violence of widespread fire enveloping cityand field in common disaster, let who will take it.

6 What more do I owe life than to encourageit on its journey, and to despatch it with goodwishes ? Go resolutely, go prosperously ! Theremust be no hesitation in rendering back life. Itis merely a question of time, not of fact. Whatyou are doing must be done some day. Beseech

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not nor fear, nor draw back as if starting toface some peril. Nature, who bore you, waitsyour coming to a place better and safer thanearth. There is no earthquake there, friend, no 7winds clashing with loud noise of cloudy sky, nofires to waste province and city, no fear of shipwreck swallowing up whole fleets, no armies arrayed with opposing banners, or common fury ofhosts prepared for mutual destruction, no plague,no pyres lit up around the promiscuous resting-place of slaughtered nations. If death is a lightaffair, why fear it? If it is heavy, then rather let itfall once for all than be always hanging over us.Should / fear to perish when earth must perish sbefore me, when the powers that shake are shaken,when they hasten to our destruction only throughtheir own? The sea received Helice and Burisentire ; shall I fear for one poor body ? Shipssail over the site of two towns, aye, towns thatwe know well, that the record preserved by lettershas brought to our intimate knowledge. Howmany others have been sunk in other places ? howmany nations has either earth or sea engulfed?Shall I rebel against my end when I know that 9I am not endless? nay, when I am fully assuredthat all things come to an end, shall I fear mylatest sigh ?

Wherefore steel yourself, Lucilius, with allyour might against fear of death. This fear it isthat drags us down ; this it is that torments anddestroys the life it tries to preserve. It magnifiesall those dangers, earthquakes and lightnings, andthe rest. You will be able to bear them allresolutely if you but reflect that short and longin life make no difference. It is but hours we lose. 10

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But suppose it is days, or months, or years, whatwe lose is, surely, bound to perish. What difference, pray, is it whether I manage to reach themor not ? Time flows on ; it leaves behind thosemost eager to seize it. Neither what is to be ismine, nor what was. I am poised upon a pointof fleeting time ; it is a great thing to have beenmoderate in one s ambitions. Laelius the Wisemade a neat retort once to a person who said, I amii sixty years old : you mean, said he, the sixty youno longer are. 1 We show our failure to grasp theterms of this elusive life of ours, and the conditions oftime that is never our own, in reckoning up as oursyears that are now lost. Let us fix this in ourminds, and constantly remind ourselves, I must die.When ? What matter is that to you ? Death is alaw of nature ; death is a tribute and a duty imposedon mortals ; it is the remedy of all ills. Whoevernow fears it will one day long for it. Giving up allelse, Lucilius, make this your one meditation, notto dread the name death. By long reflection makedeath an intimate friend, that, if so required, youmay be able even to go forth to welcome it.

1 It is almost impossible to express in English the play onFrench is more amenable. "J ai soixante ans ! Parlez-vous des soixanteans que vous n avez plus ? " NISARD.